added view controller for storage choice
added buttons for storages choices

 * iCloud and Trello are disabled, because no implementation exists
Merge branch 'master' into add-screen-for-storage-choice
added new storage choice class

 * added prepare for segue, to set the localStorage in the table view
added storage selection controller class to view
added localStorage attribute
added check for localStorage to save it correct
added localstorage check, to save it correct
added storage naming in nav bar and save screen
corrected navigation with back button
corrected selectStorage segue

 * disabled nav bar in selectStorage view
add nav bar in todo table view

 * moved nav bar title to viewDidLoad
re-added "Add"-button
Merge pull request #2 from rombald/add-screen-for-storage-choice

[WIP] Add storage choice view